Foot warts or plantar warts (verrucae) are caused by strains of the human papilloma virus (HPV). Foot warts are skin lesions that usually occur on the bottom or plantar surface of the foot. Differentiating foot warts from other skin lesions on the bottom of the foot can be difficult. Foot warts occur in an estimated 7% – 10% of the population with a higher incidence in children.
Viruses are made up of genetic fragments encased in protein capable of inserting itself into a cell. Viruses bind to there target cells by latching on to certain receptors specific to the cell they are infecting, they then harness our cells to reproduce. During this process, they must trick our bodies cells into creating and feeding the cells infected by the virus, or the infection will not be successful and our bodies will battle the infection.
The viral infect increases the needed reproductive rate of the cells infected with the virus, so the virus releases factors calling for more blood supply, so new capillaries form. Because viruses infect our skin cells, we must kill the cells they infect in order to destroy the wart.
Diagnosing Plantar Warts
There are two types of foot warts – simple and mosaic. Simple warts have a single capillary feeding the infected dermal cells and are typically respond better to treatments. Mosaic warts are colonies of simple warts, there are multiple capillaries feeding the infected cells and difficult to resolve.
Diagnosing plantar warts can be difficult even for an experienced physician. There are other skin lesions that may have all or some of the common characteristics of plantar warts. Here are some key characteristics when diagnosing plantar warts:
- have small identifiable black dots called petechiae
- interrupt the normal skin lines
- Pain with lateral compression (pinching) the area
Treatment of Plantar Warts
There are many different treatment options for plantar warts, topical caustic agents, surgical excision, cryotherapy (freezing), laser destruction, injections, and stimulating the body’s immune system. Most of the topical agents available over the counter (OTC) are ineffective. The OTC topicals are not strong enough to exfoliate the skin at a rate capable destroying the infected dermal cells which lie deep below the thickened skin. Cryotherapy can be effective, however liquid nitrogen is far more effective than the at home “cold spray cans” advertised on TV. The cold cans are not capable of reaching cold enough temperatures to freeze the skin effectively. Laser Treatment has become the treatment of choice, it attacks the warts blood supply and destroys the cells infected by the virus.
The below images are are from a case of suspected verrucous carcinoma, the patient did not follow up for biopsy.